Humidity activated materials having shape-memory

ABSTRACT

The present invention relates to shape deformable materials, which are capable of (1) being deformed, (2) storing an amount of shape deformation, and (3) recovering at least a portion of the shape deformation when exposed to a humid environment. The shape deformable materials can advantageously be in the form of films, fibers, filaments, strands, nonwovens, and pre-molded elements. The shape deformable materials of the present invention may be used to form products, which are both disposable and reusable. More specifically, the shape deformable materials of the present invention may be used to produce products such as disposable diapers, training pants, incontinence products, and feminine care products.

FIELD OF THE INVENTION

[0001] The present invention relates to materials having a shape memorywhich is activated when the products are exposed to high humidity ormoist environments.

BACKGROUND OF THE INVENTION

[0002] Disposable absorbent products are typically subjected to one ormore liquid insults, such as of water, urine, menses, or blood, duringuse. As such, the outer cover backsheet materials of the disposableabsorbent products are typically made of liquid-insoluble and liquidimpermeable materials, such as polypropylene films, that exhibit asufficient strength and handling capability so that the disposableabsorbent product retains its integrity during use by a wearer and doesnot allow leakage of the liquid insulting the product.

[0003] Although current disposable and reusable garments have beengenerally accepted by the public, these products still have the need ofimprovement in specific areas. For example, many absorbent products havea tendency to lose their shape or become uncomfortable to wear after theproducts are subjected to liquid insults and in-use conditions of highhumidity and body temperature. Such changes in shape often result in illfitting absorbent products and/or leakage.

[0004] Typically elastomeric materials are incorporated into disposableand reusable products to improve the fit of the products and preventleakage during use. These elastomeric materials may be attached to thedisposable product by several methods. At one time, elastic was appliedto the substrate by sewing. (See U.S. Pat. No. 3,616,770 to Blyther etal.; and U.S. Pat. No. 2,509,674 and RE 22,038 to Cohen). A newer methodfor attaching elastomeric material to a substrate is by use of anadhesive. (See U.S. Pat. No. 3,860,003 to Buell.) Welding, such as sonicwelding, has also been used to attach elastomeric material to adisposable product. (U.S. Pat. No. 3,560,292 to Butter). Laminateshaving an elastomeric layer and a co-extensive skin layer have also beenused. (U.S. Pat. No. 5,429,856 to Kruger et al.).

[0005] However, these methods of attachment present several problems.First is the problem of how to keep the elastic in a stretched conditionwhile applying the elastic to the substrate. Another problem is thatattachment of a ribbon of elastomeric material will concentrate theelastomeric force in a relatively narrow line. This may cause theelastic to pinch and irritate the wearer's skin. (See U.S. Pat. Nos.3,860,003; 4,352,355; and 4,324,245 to Musek et al.; U.S. Pat. No.4,239,578 to Gore; and U.S. Pat. Nos. 4,309,236 and 4,261,782 to Teed.)Other disadvantages of conventional attachment methods include speed,ease of manufacture, and cost. More importantly, difficulties may beencountered in maintaining a uniform tension on the elastic layer duringits attachment to the substrate and also in handling the shirred articleonce the elastic layer is relaxed.

[0006] Heat-responsive elastomeric films overcome some of thesedetriments. Heat-responsive elastomers exist in two forms: athermally-stable and a thermally-unstable form. The thermally-unstableform is created by stretching the material while heating near itscrystalline or second phase transition temperature, followed by a rapidquenching to freeze it in the thermally-unstable, extended form. Theelastomeric film can then be applied to a disposable product, forexample a diaper, and heated to shirr or gather the elastomericmaterial, thereby producing a thermally-stable form of the elastomericmaterial. Examples of heat-responsive elastomeric films are disclosed inU.S. Pat. No. 4,681,580 to Reising et al., U.S. Pat. No. 4,710,189 toLash, U.S. Pat. No. 3,819,401 to Massengale et al., U.S. Pat. No.3,912,565 to Koch et al., and U.S. Pat. No. RE 28,688 to Cook.

[0007] These polymers have several disadvantages. The first of thesedisadvantages involves the temperature to which the elastomeric materialmust be heated to stretch the material to its thermally-unstable form.This temperature is an inherent property of the elastomeric material.Therefore, the disposable product is often difficult to engineer becausetemperatures useful for the production of the overall product may not becompatible with the temperature necessary to release thethermally-unstable form of the elastomer. Frequently, this temperatureis rather high and can be detrimental to the adhesive material used toattach the various product layers. Another drawback to the use ofheat-responsive elastomers is that they can constrain the manufacturingprocess, rendering it inflexible to lot variations, market availability,cost of raw materials, and customer demands.

[0008] U.S. Pat. No. 4,820,590 to Hodgkin et al. describes anelastomeric blend of three components to reduce the temperature requiredfor the material to resume its heat stable form. Additionally, GB Patent2,160,473 to Matray et al. proposes an elastomer which will shrink at anelevated temperature, for example at or above 170° F. The advantageousfeatures of these materials, compared to the heat-shrinkable materialsdiscussed above, is that it does not require preheating during thestretching operation, but rather can be stretched at ambienttemperatures by a differential speed roll process or by “cold rolling.”

[0009] Problems with use of these elastomers include difficultiesinherent in applying a stretched elastic member to a flexible substratesuch as a disposable diaper. Although some of the elastomers proposedhave the advantage that they can be applied at ambient conditions in ahighly stretched, unstable form, subsequent, often extreme, heating isrequired to release the thermally-unstable form to a contractedthermally-stable form. The temperature of this heat release is generallyinflexible since it is determined at the molecular level of theelastomer. Thus, selection of materials for the disposable product whichare compatible with this heating step is required.

[0010] Further, when individual heat activated elastic materials areused, the heat activation is generally accomplished by passing thegarments through a heated air duct for a period of time. Since thermalheating must be transferred from an outer surface of the garment toinner portions of the garment, distribution of the activation means(i.e., thermal heat) throughout the garment takes considerable amountsof time and energy, resulting in an inefficient activation process. As aresult, such heating processes can consume vast amounts of energy andundesirably result in slower manufacturing speeds.

[0011] What is needed in the art is a method of activating a shapedeformation of a material without using an inefficient thermal heatingactivation process. What is also needed in the art is a method ofactivating a shape deformation of a material without substantiallyincreasing the temperature of the material. Furthermore, there is a needfor new materials that may be used in disposable absorbent products thatgenerally retain their integrity during use, are easily disposed of, andhave the ability to change to a desired shape and/or texture duringin-use conditions. For example, upon exposure to a high humidityenvironment, the disposable product may transform to a desired productconfiguration which will guard against leakage.

SUMMARY OF THE INVENTION

[0012] The present invention addresses some of the difficulties andproblems discussed above by the discovery of a humidity activatedmaterial which changes shape, aspect ratio, or length when the materialis exposed to a humid environment. The material is capable of beingdeformed in at least one spatial dimension when exposed to one or moreexternal forces, is capable of maintaining a degree of deformation in atleast one spatial dimension once the external force is removed, and iscapable of exhibiting a change, or percent recovery, in at least onespatial dimension when subjected to a humid or moist environment. Thehumid or moist environment may be created by in-use conditions ofabsorbent products.

[0013] More particularly, the humidity responsive material contains atleast one shape deformable matrix material. The shape deformable matrixmaterial typically contains a polymer, such as a segmented blockcopolymer having one or more hard segments and one or more softsegments. Either the soft segment, the hard segment, or both containfunctional groups or receptor sites that are responsive to humidity.

[0014] Still more particularly, the shape deformable matrix material maycontain a blend of an elastomeric polymer and a non-elastomeric polymer.The non-elastomeric polymer may be a moisture absorbing polymer thatexhibits at least a 20% reduction in modulus when the material isexposed to a humid environment. The humidity responsive material of thepresent invention finds applicability in a number of products, includingproducts containing a gatherable or elastic part.

[0015] These and other features and advantages of the present inventionwill become apparent after a review of the following detaileddescription of the disclosed embodiments and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is further described by the accompanyingdrawings, in which:

[0017]FIG. 1 representatively shows a top plan view of a compositematerial according to one embodiment of the present invention; and

[0018]FIG. 2 representatively shows a partially cut away, top plan viewof an absorbent article according to one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention addresses some of the difficulties andproblems discussed above by the discovery of materials which are capableof exhibiting a shape deformation when exposed to humidity, and methodsof using the same. These materials exhibit a change in at least onespatial dimension when subjected to high humidity or a moistenvironment. Unlike known materials and methods, the materials andmethods of the present invention maximize the amount of “locked-in”shape deformation within the material, as well as, maximize the percentchange in one or more spatial dimensions of the material. Further,unlike previous recovery methods which involve a heating step, thepresent invention is directed to a method of causing a change in one ormore spatial dimensions of the material without a substantial change inthe temperature of the material. The recovery method of the presentinvention instead includes subjecting the material to a level ofhumidity or moisture sufficient to cause a desired change in one or morespatial dimensions without a substantial change in the temperature ofthe material. The materials and methods of the present invention findapplicability in a number of products and processes.

[0020] One method of measuring the change in one or more spatialdimensions of a material is given by the equation below:${\% \quad R} = {\frac{\left( {\delta_{i} - \delta_{f}} \right)}{\delta_{i}} \times 100}$

[0021] wherein:

[0022] % R represents the percent change, or the percent recovery, ofone spatial dimension of the material;

[0023] δ_(i) represents the dimension prior to subjection to humidityactivitation; and

[0024] δ_(f) represents the dimension after subjection to the humidityactivation.

[0025] The above equation may be used to determine the percent recoveryof one or more spatial dimensions of the shape deformable material ofthe present invention. Further, the above equation may be used on anymaterial capable of experiencing a change in a spatial dimension.Suitable materials having a shape deformation and a desired percentrecovery are given below.

[0026] Shape Deformable Material Components

[0027] The present invention is directed to shape deformable materials,which exhibit a change in at least one spatial dimension when subjectedto a humid environment. Suitable materials include any material or blendof materials, which has the following properties: (1) is capable ofbeing deformed in at least one spatial dimension when exposed to one ormore external forces, (2) is capable of maintaining a degree ofdeformation in at least one spatial dimension once the external force isremoved, and (3) is capable of exhibiting a change, or percent recovery,in at least one spatial dimension when subjected to a humid environment.

[0028] The shape deformable materials of the present invention are“humidity softenable”. As used herein, the term “humidity softenable” ismeant to refer to a material which when placed in a humid environmentcan dramatically reduce its stiffness and modulus, at least about 20%,and/or relax as a result of moisture absorption from the environment.Preferably, when subjected to a humid environment, the shape deformablematerial has a reduction in stiffness and modulus of at least about 30%,and more preferably at least about 50%. The term “modulus” as usedherein, is meant to refer to the elastic tensile modulus calculatedaccording to ASTM Standard D882-95a, which is incorporated herein byreference. Generally, the elastic tensile modulus is calculated bydividing the tensile stress of the polymer by the corresponding strain.

[0029] The shape deformable materials of the present invention maycontain one or more of the following classes of components:

[0030] Shape Deformable Matrix Materials

[0031] The shape deformable materials of the present invention containat least one shape deformable matrix material. As used herein, the term“shape deformable matrix material” is used to describe a material havingthe above-mentioned properties, and is also capable of encompassing oneor more filler materials. Suitable shape deformable matrix materialsinclude, but are not limited to polymers.

[0032] In one embodiment of the present invention, the shape deformablematrix material contains at least one polymer, and more preferably twopolymers. Suitable polymers include, but are not limited to, segmentedblock copolymers comprising one or more hard segments and one or moresoft segments; polyester-based thermoplastic polyurethanes;polyether-based polyurethanes; polyethylene oxide; poly(ether ester)block copolymers; polyamides; poly(amide esters); poly(ether amide)copolymers; polyvinyl alcohol; polyvinyl pyrolidone; polyvinyl pyridine;polyacrylic acid; polymethacrylic acid; polyaspartic acid; maleicanhydride methylvinyl ether copolymers of varying degrees of hydrolysis;polyvinyl methyl ether copolymers of polyacrylic acid and polyacrylicesters; and mixtures thereof. Desirably, the shape deformable matrixmaterial contains a segmented block copolymer comprising one or morehard segments and one or more soft segments, where either the softsegment, the hard segment, or both contain functional groups or receptorsites that are responsive to humidity.

[0033] As used herein, the phrase “responsive to humidity” is used todescribe functional groups and/or receptor sites within a polymer,which, when exposed to a humid environment enables a desired amount ofshape recovery of a shape deformed polymer. As used herein, the phrase“humid environment” or “humidity” refers to an environment having atleast 50% relative humidity. Suitable functional groups and/or receptorsites include, but are not limited to, functional groups such as urea,amide, nitro, nitrile, ester, ether, hydroxyl, ethylene oxide, and aminegroups; carboxylic acid salts, and sulfuric acid salts; ionic groups,such as sodium, zinc, and potassium; and receptor sites having anunbalanced charge distribution formed from one or more of the abovegroups. Desirably, the functional groups contain one or more functionalgroups having a high dipole moment (i.e., greater than about 1.5 Debye)such as urea, amide, nitro, and nitrile groups.

[0034] More desirably, the segmented block copolymer is an elastomer.Suitable shape deformable elastomers for use in the present inventioninclude, but are not limited to, polyurethane elastomers, polyetherelastomers, poly(ether amide) elastomers, polyether polyesterelastomers, polyamide-based elastomers, thermoplastic polyurethanes,poly(ether-amide) block copolymers, thermoplastic rubbers such asuncrosslinked polyolefins, styrene-butadiene copolymers, siliconrubbers, synthetic rubbers such as nitrile rubber, butyl rubber,ethylene-vinyl acetate copolymer, styrene isoprene copolymers, styreneethylene butylene copolymers and mixtures of thereof. Somenon-elastomeric polymers may be used. These polymers can provide somedegree of recovery when exposed to humidity. Examples of non-elastomericpolymers useful in the present invention include, but are not limitedto, polyethylene oxide, copolymers of polylactic acid, blends andmixtures thereof.

[0035] In one embodiment of the present invention, the shape deformablematrix material contains a polyurethane. Suitable polyurethanes for usein the present invention include, but are not limited to,polyester-based aromatic polyurethanes, polyester-based aliphaticpolyurethanes, polyether-based aliphatic and aromatic polyurethanes, andblends and mixtures of these polyurethanes. Such polyurethanes may beobtained, for example, from Huntsman Polyurethanes (Chicago, Ill.).Examples of specific polyurethanes, which can be used in the presentinvention include, but are not limited to, MORTHANE® PS370-200,MORTHANE® PS79-200, MORTHANE® PN3429, and MORTHANE® PE90-100. Otherthermoplastic polyurethanes applicable for the present invention can beobtained from BF Goodrich Performance Materials under the trade nameESTANE® polyurethanes.

[0036] In a further embodiment of the present invention, the shapedeformable matrix material includes a poly(ether amide) elastomer.Poly(ether amide) elastomers, which may be used in the presentinvention, may be obtained, for example, from Elf Atochem North America,Inc. (Philadelphia, Pa.). Examples of such poly(ether amide) elastomersinclude, but are not limited to, PEBAX®2533, PEBAX®3533, and PEBAX®4033.

[0037] Polyurethane elastomers and poly(ether amide) elastomers areparticularly useful as the shape deformable matrix material in thepresent invention because they structurally consist of soft and hardsegments, which contain groups having high dipole moments (i.e.,isocyanate, amide, and ester groups) which are sensitive to humidity. Inaddition, due to the high polarity of the high dipole moments, theseelastomers are easily blended or combined with a humidity sensitivecomponent. For example, the humidity sensitive component may be blendedwith the elastomer or otherwise incorporated into the molecularstructure of the elastomer. The hard segments in these elastomerstypically act as physical cross-linking points for the soft segments,enabling an elastomeric performance. Both hard and soft segments maycontribute to the shape deformation during a number of pre-activationtreatments described below, such as stretching, which provides“locked-in” shape deformation, which may be recoverable by exposure to ahumid environment.

[0038] In still another embodiment of the present invention, the shapedeformable matrix material includes a blend of an elastomeric polymerand a non-elastomeric polymer. These blends may either be co-extrudedtogether, or may be formed into multi- or micro-layer structures.Alternatively, the multi-layer or micro-layer structure may be formedfrom separate layers of the elastomeric polymer and non-elastomericpolymer. These layers may or may not be alternating layers. Blends areadvantageous since blending or multi-layering/micro-layering of a shapedeformation elastomer with another non-elastomeric shape deformationpolymer can improve latent deformation properties, especially at lowerstretching temperatures, and can significantly increase recoverabledeformation as a result of activation by humidity.

[0039] For example, the shape deformable matrix material may contain anelastomeric polymer, and a non-elastomeric polymer such as a moistureabsorbing polymer, which can soften and relax as a result of moistureabsorption. The elastomeric polymer provides force for the dimensionalchange when the moisture absorbing polymer is softened and relaxed. Themoisture absorbing polymer is “humidity softenable”. The moistureabsorbing polymer can dramatically reduce its stiffness and modulus, atleast about 20%, and/or relax as a result of moisture absorption fromthe environment. Preferably, when subjected to a humid environment, themoisture absorbing polymer has a reduction in stiffness and modulus ofat least about 30%, and more preferably at least about 50%. Elevatedtemperatures, including exposure to body temperature, can facilitatemoisture absorption.

[0040] In addition, the rate of moisture absorption can vary which canprovide a control over time-dependent response.

[0041] The blend should contain an amount of moisture absorbing polymerwhich will be effective in achieving the desired humidity activatedshape. The humidity softenable polymer will be present in the shapedeformable matrix material in an amount from greater than 0 to less than100 weight percent. Preferably, the shape deformable matrix materialcontains from about 5% to about 90% by weight moisture absorbingpolymer. More preferably, the material contains from about 10% to about60% by weight moisture absorbing polymer. Examples of suitable moistureabsorbing polymers include, but are not limited to polyethylene oxide,polyethylene glycol, polyvinyl alcohol, polyvinyl pyrolidone, polyvinylpyridine, or mixtures thereof. Preferably, the moisture absorbingpolymer is polyethylene oxide. The moisture absorbing polymer shouldhave an ability to be stretched or otherwise plastically deformed tolock in a deformation and/or shape change which can be released laterwhen the polymer is softened in a humid environment.

[0042] The elastomeric polymer present in the blend should have theability to be stretched or deformed from its original length and toretract upon the release of the stretching or deformation force. Theelastomeric polymer may have permeability for water vapor which canfacilitate moisture absorption by the humidity-softenable polymer. Theelastomeric polymer component of the shape deformable matrix materialshould be present in an amount which is effective to achieve the desireddimensional change properties. The elastomeric polymer will be presentin the shape deformable matrix material in an amount from greater than 0to less than 100 weight percent. Preferably, the shape deformable matrixmaterial contains from about 10% to about 95% by weight elastomericpolymer. More preferably, the material contains from about 50% to about70% by weight elastomeric material. Examples of suitable elastomericpolymers include, but are not limited to thermoplastic polyurethanes,poly(ether-amide) block copolymers, thermoplastic rubbers such asuncrosslinked polyolefins, styrene-butadiene copolymers, siliconrubbers, synthetic rubbers such as nitrile rubber, styrene isoprenecopolymers, styrene ethylene butylene copolymers, butyl rubber, nyloncopolymers, spandex fibers comprising segmented polyurethane,ethylene-vinyl acetate copolymer or mixtures thereof. Preferably, theelastomeric polymer is polyurethane.

[0043] The moisture absorbing polymer and elastomeric polymer may becombined by any method known in the art. For example, the polymers maybe mixed, blended, laminated, coextruded, microlayered, or fiberized ina core-shell structure or in a side by side structure. Depending on theratio of the elastomeric polymer and the moisture absorbing polymer, theblend can demonstrate elastomeric properties or the properties of aductile thermoplastic polymer.

[0044] Non-Activatable Materials

[0045] As used herein, the term “non-activatable materials” is used todescribe any material, which lacks one or more of the three propertiesmentioned above when describing suitable shape deformable materials.Suitable non-activatable additional materials include, but are notlimited to, non-elastomeric polymers, tackifiers, anti-blocking agents,fillers, antioxidants, UV stabilizers, polyolefin-based polymers andother cost-saving additives that may be added or blended to addbeneficial properties.

[0046] The amount of non-activatable material blended with theabove-mentioned shape deformable polymers may vary as long as theresulting blend possesses a desired amount of shape deformationproperties. The blend may contain from about 40 to 99.5 weight percentof shape deformable polymer and from about 60 to 0.5 weight percent ofadditional non-activatable materials. Desirably, the blend contains fromabout 60 to 99.5 weight percent of shape deformable polymer and fromabout 40 to 0.5 weight percent of additional materials. More desirably,the blend contains from about 80 to 99.5 weight percent of shapedeformable polymer and from about 20 to 0.5 weight percent of additionalnon-activatable materials.

[0047] Configuration of Shape Deformable Materials

[0048] The shape deformation materials of the present invention maypossess a variety of shapes and sizes. The shape deformation materialsof the present invention may be in the form of blends, films,multi-layered or micro-layered films, laminates, filaments, fabrics,foams, nonwovens or any other three-dimensional form. In manyembodiments, particularly for use in personal care products, a preferredsubstrate is nonwoven material. As used herein, the term “nonwovenmaterial” refers to material that has a structure of individual fibersor filaments randomly arranged in a mat-like fashion. Nonwoven materialmay be made from a variety of processes, including, but not limited tospunbond processes, meltblown processes, air-laid processes, wet-laidprocesses, hydroentangling processes, staple fiber carding and bonding,and solution spinning.

[0049] The shape deformation material may be formed by any method knownto those of ordinary skill in the art including, but not limited to,extrusion, coating, foaming, etc. In addition, the shape deformationmaterial may be formed by blending or combining a material with ahumidity responsive component. Alternatively, a humidity responsivecomponent may be incorporated into the molecular structure of a compoundto produce the shape deformation material. There is no limitation on thesize of the shape deformation material; however, the amount of shapedeformation and the percent recovery of the shape deformation materialmay be limited if the size of the material is too great.

[0050] In an alternative embodiment, materials that include a blend oftwo shape-deformable polymers or a multi- or micro-layer structurehaving two shape-deformable polymers demonstrate that blending ormulti-layering/micro-layering of a shape deformation elastomer withanother non-elastomeric shape deformation polymer can improve latentdeformation properties, especially at lower stretching temperatures, andcan significantly increase recoverable deformation as a result ofactivation by humidity.

[0051] Regardless of the size and shape of the shape deformationmaterial, the shape deformation material of the present inventionexhibits a change in at least one spatial dimension when subjected to ahumid environment. Typically, the shape deformation material of thepresent invention exhibits a change in one, two, or three dimensions.For example, when the shape deformation material is in the form of afiber, the shape deformation material exhibits a change in the fiberlength and/or fiber diameter. When the shape deformation material is inthe form of a film, the shape deformation material exhibits a change inthe film length and/or film width and film thickness. A percent recoverymay be measured for each of the dimensions of the shape deformationmaterial.

[0052] As can be seen by the above equation, in order to maximize thepercent recovery of a given dimension, % R, the difference between thedimension prior to (δ_(i)) and after subjection to humidity activation(δ_(f)) needs to be maximized. The present invention provides a methodof maximizing the percent recovery, % R, of a given dimension of amaterial. One factor, which effects the ability to maximize the presentrecovery of a given dimension, is the ability to “lock-in” a desiredamount of shape deformation in the material prior to subjecting thematerial to humidity.

[0053] Preparation of Materials Having a Degree of Shape Deformation

[0054] One aspect of the present invention is directed to a method ofpreparing materials having a desired amount of “locked-in” shapedeformation. As used herein, the term “locked-in shape deformation”refers to a recoverable amount of shape deformation in one or morespatial dimensions of a given material, resulting from one or moreforces exerted on the given material. Suitable forces include, but arenot limited to, stretching, heating, cooling, compressing, bending,coiling, shearing, etc. The amount of locked-in shape deformation mayvary depending upon a number of factors including, but not limited to,the material composition, the material temperature, the materialtreatment procedures (i.e., the amount of stress administered to thematerial), and any post-treatment procedures (i.e., quenching, tension,etc.). A number of factors, which may contribute to the locked-in shapedeformation of a given material are discussed below.

[0055] Stretching or Compressing

[0056] Stretching and compressing are ways to impart a locked-in shapedeformation to a shape deformation material of the present invention.The amount of deformation resulting from stretching or compressing isdependent upon a number of variables. Important variables associatedwith stretching or compressing of a given material include, but are notlimited to, the stretch or draw ratio, the stretching or compressingtemperature, the stretching or compressing rate, and post-stretching orpost-compressing operations, if any, such as heat setting or annealingoperations.

[0057] Additionally, other types of deformation may be used besidesstretching and compressing including, but not limited to, bending,twisting, shearing, or otherwise shaping the material using complexdeformations.

[0058] Stretch or Draw Ratio

[0059] The amount of locked-in shape deformation that can be imparted toa given material depends upon the stretch or draw ratio. In general, theamount of locked-in shape deformation of a material is typically largerwhen the draw ratio is larger. Stretching of the material may beaccomplished in one or more directions, such as uniaxial or biaxialstretching. Stretching in more than one direction, such as biaxialstretching, may be accomplished simultaneously or sequentially. Forexample, when sequential biaxial stretching a film of shape deformationmaterial, the first or initial stretching can be conducted in either themachine direction (MD) or the transverse direction (TD) of the filmmaterial.

[0060] In one embodiment of the present invention, the shape deformationmaterial desirably possesses a draw or stretch ratio of at least 1.5 inone or more directions. More desirably, the material possesses a draw orstretch ratio in one or more directions of from about 2 to about 10.Even more desirably, the material possesses a draw or stretch ratio inone or more directions of from about 3 to about 7. Lower draw ratios mayresult in low shape deformation and low recoverable deformation.However, low draw ratios may be applicable to some embodiments of thepresent invention, depending on specific applications and the desiredamount of shape deformation. Very high draw ratios during the process ofimparting shape-deformation memory may result in a partial loss of shapememory as a result of unrecoverable plastic deformations in thematerial.

[0061] Stretching Temperature

[0062] During stretching, the material sample may be optionally heated.Desirably, stretching is conducted at temperatures below the meltingtemperature of the material. In one embodiment of the present inventionwherein the material is a polymeric material, the drawing temperature isnot more than about 120° C. and, desirably, not more than about 90° C.When the drawing temperature is too high, the material can melt, becomeexcessively tacky, and/or become difficult to handle. In addition,excessively high stretching temperatures can cause irreversibledeformations in which the shape deformation of the material is lost andthe original shape is not recoverable.

[0063] Stretching a given material at low temperatures may result in alower amount of locked-in shape deformation and low percent recoveryduring activation. Generally, when the shape deformation materialcontains segmented block thermoplastic elastomers, it is desired tostretch the material near the softening or glass transition temperatureof the hard segments. In some cases, when the soft segments experiencestrain induced crystallization during stretching, drawing the materialnear the crystalline transition temperature of the soft segments isdesired. This is the case, for example, when the shape deformationmaterial is a PEBAX® elastomer.

[0064] Stretch Rate

[0065] The rate at which stretching is performed may also affect theamount of locked-in shape deformation imparted to a given shapedeformation material. Suitable stretching rates will vary depending uponthe material to be stretched. As a general rule, stretching may beaccomplished at rates of at least about 50%/min. and as much as about5000%/min. Desirably, the stretching rate is from about 100%/min. toabout 2500%/min. Higher stretching rates may be more beneficial forprocess efficiency; however, very high stretching rates may result in amaterial failure at reduced draw ratios. The effect of stretching rateon locked-in shape deformation is dependent upon the structure andcomposition of the material. For some embodiments of the presentinvention, such as when the shape deformation material contains athermoplastic polyurethane, the stretching rate does not have asignificant impact on the resulting amount of locked-in shapedeformation.

[0066] Post-Stretching Operations

[0067] The locked-in shape deformation properties of a shape deformationmaterial of the present invention may be affected by post-stretchingoperations. A number of factors should be considered duringpost-stretching operations including, but not limited to, the materialcomposition, the relaxation tendency of the material, and the desiredamount of percent recovery for a particular application.

[0068] Relaxation Tendency

[0069] In most cases, the shape deformation material will possess atendency to return to its original, pre-stretched configuration. Thisproperty may be described as a relaxation tendency. Although therelaxation tendency may vary from material to material, generally, theamount of relaxation tendency increases as the elasticity of thematerial increases. Further, the amount of relaxation tendency increasesfor a given material as the temperature of the material increases.

[0070] Tension

[0071] During post-stretching operations, the stretched material may beheld under tension in a stretched state, gradually released from astretched state over time, or treated in some manner while in atensionless state. Typically, recoverable shape deformation or percentrecovery is larger when the shape deformation material is held in astretched state for a longer period of time. When the shape deformationmaterial is a polymeric fiber or film, the shape deformation material isdesirably held in a stretched state for at least about 30 seconds. Moredesirably, the shape deformation material is held in a stretched statefor at least about ten minutes. Even more desirably, the shapedeformation material is held in a stretched state for at least about onehour, and most desirably, about 24 hours. The time under tension dependson a molecular structure of the shape deformation polymer. Forpoly(ether amide) shape deformation elastomer, e.g. PEBAX® elastomer,the material can be held under tension for a very short period of time.For polyester aromatic and aliphatic polyurethanes with shapedeformation, e.g. MORTHANE® polyurethanes, a longer time under tensionis preferred. The use of tension, especially in combination withtemperature, may be useful to preserve orientation in the shapedeformation material and protect the resulting structure againstundesirable shrinkage after stretching.

[0072] Temperature

[0073] The stretched shape deformation material may be subjected topost-stretching operations at room temperature or at elevatedtemperatures. The “setting” process (i.e., the process of locking-in adesired amount of stretch) may be conducted in accordance with aselected, predetermined temperature-time profile, which is dependent onthe structure of the shape deformation material and the relaxationtendency of the shape deformation material. In general, the settingprocess is conducted at temperatures below the melting temperature ofthe shape deformation material. Desirably, the setting process isconducted at temperatures above the temperature of secondary relaxationprocesses and temperatures above the glass transition temperature of thesoft segments in segmented block elastomers. This allows the structureto relax during the setting process and reduce relaxation tendency,which can result in increased shape deformation

[0074] Other Post-Stretching Operations

[0075] Other additional post-stretching processes or operations, such asUV treatment, ultrasonic treatment, high energy treatment, orcombinations of these treatments, may be incorporated into thepost-stretching process to enhance the latent deformation by modifyingthe morphological state of the stretched material and maximizing thepercent recovery of the shape deformation material upon activation.

[0076] The Activation Process

[0077] The present invention is further directed to a method of causingthe efficient recovery of at least a portion of the latent, locked-inshape deformation of the above-described shape deformation materials.The method includes subjecting the shape deformation material to anamount of humidity or moisture in order to effect a substantial change(i.e., recovery) in at least one spatial dimension of the material. Themethod may be used to cause the shape deformation of the above-describedshape deformation material itself or a product containing as one or morecomponents the above-described shape deformation material.

[0078] Recovery of latent, locked-in shape deformation of the shapedeformation material of the present invention is accomplished byexposing the shape deformation material to an environment having atleast a 50% relative humidity. Desirably, the humid environment has atleast a 75% relative humidity, and more desirably at least a 85%relative humidity.

[0079] The shape deformation material of the present invention may beexposed to a sufficient amount of humidity to effect a change in atleast one spatial dimension of the material.

[0080] Percent recovery may vary depending on a number of factorsincluding, but not limited to, the shape deformation material; theamount of latent, locked-in shape deformation; the pre-activationtreatments used to prepare the shape deformation material; and thedesired amount of percent recovery for a particular application. Formost applications, the percent recovery (% R) is desirably greater thanabout 30% upon exposure to a humid environment. For most applications,the percent recovery (% R) is more desirably greater than about 60% uponexposure to a humid environment. A preferred range of the percentrecovery is from about 15% to about 75% upon exposure to a humidenvironment.

[0081] As discussed above, the use of humidity or moisture in thepresent invention to activate shape deformation materials isadvantageous over conventional methods, which use thermal energy, for anumber of reasons. The use of humidity enables rapid molecularreorientation (i.e., recovery) of a shape deformable material having alatent, locked-in amount of shape deformation without a substantialincrease in the temperature of the shape deformable material. As usedherein, “a substantial increase in the temperature of the shapedeformable material” refers to an increase in temperature of greaterthan about 15° C. Desirably, the shape deformable material exhibits adesired percent recovery while experiencing a temperature change of lessthan about 12° C.

[0082] As opposed to conventional recovery methods, which desire thermalheating of a shape deformable material, the activation process of thepresent invention desirably minimizes the degree of heating of the shapedeformable material. Further, the activation process of the presentinvention results in no surface overheating of the shape deformationmaterial, reduced material degradation, and energy savings.

[0083] In some conventional processes, the recovery of shape deformationis achieved by heating a shape deformable material to temperatures belowthe melting temperature of the stretched polymer material and above thestretching temperature. Low recovery temperatures may result in lowrecoverable deformation, while excessively high temperatures may resultin melting of the shape-deformed material. However, in the presentinvention using humidity, the temperature of the environment is notcritical. The temperature of the environment surrounding the shapedeformable material of the present invention may vary depending on thedesired conditions in a given room or the in-use conditions of a garmentcontaining the shape deformable material. For example, the activationprocess of the present invention may be performed at room temperature orin a cooled or heated zone.

[0084] Compared to conventional systems, which have used heated air orheated rolls to activate webs or individual pieces of latent elasticmaterial, the use of humidity during in-use conditions is lessexpensive. Alternatively, in a manufacturing process for absorbentarticles, the entire article may be manufactured and packaged while theshape deformation material of the absorbent article is in a latentstate. Prior to shipping the articles, the shape deformation materialwithin the absorbent article may be activated by humidity.

[0085] Articles of Manufacture

[0086] The present invention is further directed to articles ofmanufacture, which contain the above-described shape deformablematerials. The shape deformable material may represent a substantialpart of the article of manufacture or may represent one of manycomponents of the article. Further, the shape deformable material may beused as a single layer component or may be present as one layer of amulti-layer laminate within the article of manufacture. Suitablearticles of manufacture include, but are not limited to, productscontaining an elastic portion, such as diapers, as well as, productshaving a shrinkable, gatherable or expandable component.

[0087] In one embodiment of the present invention, the shape deformablematerial is in the form of a film, which is laminated to one or moreadditional layers to form a composite article. The additional layers mayinclude additional films, nonwoven webs, woven fabrics, foams, or acombination thereof. The resulting laminated article is suitable for usein a number of applications, such as disposable absorbent products. Suchproducts include, but are not limited to, absorbent personal care itemssuch as diapers, training pants, adult incontinence products, femininecare products such as sanitary napkins, tampons, and vaginal inserts,and health care products such as wound dressings and delivery systems.Other products include surgical drapes, surgical gowns, and otherdisposable garments.

[0088] The composite material of this embodiment is representativelyillustrated in FIG. 1. As can be seen in FIG. 1, the composite material10 includes a nonwoven web layer 12, and strips of shape deformablematerial 14 and 16, which are attached to layer 12. The strips of shapedeformable material 14 and 16 may be attached to nonwoven web layer 12by any means known to those of ordinary skill in the art. Depending onthe amount and degree of latent, locked-in shape deformation within thestrips of shape deformable material 14 and 16, activation of thecomposite material results in a desired gathered composite material.

[0089] One article of manufacture of particular interest is an absorbentgarment article representatively illustrated in FIG. 2. As can be seenin FIG. 2, the absorbent garment may be a disposable diaper 20, whichincludes the following components: a front waist section 21; a rearwaist section 22; an intermediate section 23, which interconnects thefront and rear waist sections; a pair of laterally opposed side edges24; and a pair of longitudinally opposed end edges 25. The front andrear waist sections include the general portions of the article, whichare constructed to extend substantially over the wearers front and rearabdominal regions, respectively, during use. The intermediate section 23of the article includes the general portion of the article, which isconstructed to extend through the wearer's crotch region between thelegs. The opposed side edges 24 define leg openings for the diaper andgenerally are curvilinear or contoured to more closely fit the legs ofthe wearer. The opposed end edges 25 define a waist opening for thediaper 20 and typically are straight but may also be curvilinear.

[0090]FIG. 2 is a representative plan view of a diaper 20 of the presentinvention in a flat, uncontracted state. Portions of the structure arepartially cut away to more clearly show the interior construction of thediaper 20, and the surface of the diaper which contacts the wearer isfacing the viewer. The diaper 20 further includes a substantially liquidimpermeable outer cover 26; a porous, liquid permeable bodyside liner 27positioned in facing relation with the outer cover 26; an absorbent body28, such as an absorbent pad, which is located between the outer coverand the bodyside liner; and fasteners 30. Marginal portions of thediaper 20, such as marginal sections of the outer cover 26, may extendpast the terminal edges of the absorbent body 28. In the illustratedembodiment, for example, the outer cover 26 extends outwardly beyond theterminal marginal edges of the absorbent body 28 to form side margins 31and end margins 32 of the diaper 20. The bodyside liner 27 is generallycoextensive with the outer cover 26, but may optionally cover an area,which is larger or smaller than the area of the outer cover 26, asdesired.

[0091] Shape deformable material as described above may be incorporatedinto various parts of the diaper 20 illustrated in FIG. 2. Desirably, apair of laterally opposed side strips 34 and/or a pair of longitudinallyopposed end strips 36 contain the shape deformable material of thepresent invention. Upon activation, strips 34 and 36 form gatheredportions, which provide a snug fit around the waist and leg openings ofthe diaper 20.

[0092] Optimizing Interaction of Polymer with Humidity

[0093] The present invention is also directed to a method of makingshape deformable polymers in an effort to optimize the interaction ofthe shape deformable polymer with a selected amount of humidity ormoisture. By incorporating one or more selected moieties into thepolymer backbone and/or positioning one or more selected moieties atstrategic sites along the polymer backbone of the shape deformablepolymer, one can tailor a specific shape deformable polymer, which willoptimally respond to a selected amount of humidity.

[0094] For shape deformable polymers, the efficiency of moistureabsorption is related to the permeability and solubility properties ofthe polymer. Preferably, the shape deformable polymer used in thepresent invention demonstrates high permeability to water vapor.

[0095] As discussed above with regard to functional groups within ashape deformable polymer, specifically selected moieties along thepolymer chain and the positioning of moieties along the polymer chaincan effect the level of moisture sensitivity of the shape deformablepolymer, and enhance the responsiveness of the polymer to humidity.Desirably, the presence of one or more moieties along the polymer chaincauses one or more of the following: (1) an increase in the dipolemoments of the polymer; and (2) an increase in the unbalanced charges ofthe polymer molecular structure. Suitable moieties include, but notlimited to, aldehyde, urea, amide, nitro, nitrile, ester, ether,hydroxyl, ethylene oxide, amine, carboxylic acid and sulfonamide groups,carboxylic acid salts and sulfonic acid salts.

[0096] The selected moieties may be covalently bonded or ionicallyattached to the polymer chain. As discussed above, moieties containingfunctional groups having high dipole moments are desired along thepolymer chain. Suitable moieties include, but are not limited to, urea,amide, nitro, and nitrile groups. Other suitable moieties includemoieties containing ionic groups including, but are not limited to,sodium, zinc, and potassium ions.

[0097] One example of modifying a polymer chain to enhance theresponsiveness of the polymer chain is shown below:

[0098] In the above example, a nitro group is attached to the aryl groupwithin the polymer chain. It should be noted that the nitro group may beattached at the meta or para position of the aryl group. Further, itshould be noted that other groups may be attached at the meta or paraposition of the aryl group, as shown above, in place of the nitro group.Suitable groups include, but are not limited to, nitrile groups. Inaddition to the modification shown above, one could incorporate othermonomer units into the polymer above to further enhance theresponsiveness of the resulting polymer. For example, monomer unitscontaining ethylene oxide, urea and/or amide groups may be incorporatedinto the above polymer.

[0099] In another example, polyether-type thermoplastic polyurethanewith a shape memory can contain soft blocks comprising polyethyleneoxide (PEO) blocks or segments. The molecular weight of the polyethyleneoxide segments within the polyurethane can vary from about 1000 to about100,000. Preferably the polyethylene oxide blocks or segments cancrystallize to form crystals in an ambient environment. CrystallizablePEO blocks or segments can enhance shape memory properties and increaseresponse to humidity.

[0100] A further example of designing a shape deformable polymer isgiven below, wherein one or more moieties, X and Y, are bonded tospecific sites along a block copolymer chain:

[0101] X and Y may be bonded to or otherwise incorporated in softblocks, hard blocks, or both soft and hard blocks, as well as, on theends of the polymer chain. X and Y may be randomly bonded or uniformlybonded along the polymer chain. Suitable moieties include aldehyde,ethylene oxide, ester, carboxylic acid, and sulfonamide groups. However,other groups having or enhancing unbalanced charges in a molecularstructure can also be useful; or a moiety having an ionic or conductivegroup such as, e.g., sodium, zinc, and potassium ions. However, otherionic or conductive groups can also be used.

[0102] It should be noted that moieties X and Y may also be bonded to orotherwise incorporated into the same soft or hard block within a givenpolymer chain. In one embodiment shown below, X and Y are bonded to thesame soft or hard block within a given polymer, wherein X is a moietyhaving a positive charge and Y is a moiety having a negative charge:

[0103] In such a configuration, the unbalanced charge within one polymersegment results in enhanced interaction between the polymer andhumidity, or between the polymer and a humidity sensitive component.

EXAMPLES

[0104] The following examples were conducted to produce shapedeformation materials having an amount of locked-in shape deformation,and to activate the materials. Degree of stretch/stretch ratio, stretchrate, and stretch hold/cooling rate were some of the factors consideredin order to introduce the most latent, lock-in shape deformation.

[0105] Examples 1-6 demonstrate activation of shape deformation materialusing humidity.

Example 1

[0106] A multilayer film of eight alternating layers of MORTHANE®polyurethane (PU) PS370-200 and polyethylene oxide (PEO) resin wasproduced using a microlayer coextrusion line available at Case WesternReserve University, Cleveland, Ohio. The PEO resin POLYOX® WSR-N-3000was supplied by Union Carbide Corporation in a powder form andpelletized at Planet Polymer Technologies of San Diego, Calif.Rectangular strips of multilayer PU PS370-200/PEO (50/50) film werestretched to six times their original length at 25° C. using a Sintechtensile tester. The resulting latent deformation was about 340% in filmlength. The stretched film sample was placed in an environmental ovenheld at a temperature of 37° C. and 80% relative humidity. After 20minutes in the environmental oven the sample was removed and dimensionswere measured. The dimensional change of the film in machine directionwas 32% as compared to the stretched-film length.

Example 2

[0107] The multilayer film of Example 1 was stretched to six times at25° C. using a SINTECH tensile tester. The resulting latent deformationwas about 350% in length. The stretched film sample was placed in anenvironmental oven held at a temperature of 37° C. and 95% relativehumidity. After 20 minutes in the environmental oven, the sample wasremoved and dimensions were measured. The dimensional change of the filmin machine direction was 66% as compared to the stretched-film length.

Example 3

[0108] A 50/50 blend of MORTHANE® polyurethane (PU) PS370-200 and PEOwas produced using the Haake laboratory twin screw extruder. Therectangular strips of film made of 50/50 blend were stretched to sixtimes at 25° C. The resulting latent deformation was about 185% inlength. The stretched sample was placed in an environmental oven held ata temperature of 37° C. and 95% relative humidity. After 20 minutes inthe environmental oven the sample was removed and dimensions weremeasured. The dimensional change of the film in machine direction was53% as compared to the stretched-film length.

Example 4

[0109] A microlayer film of 256 alternating layers of PU PS370-200 andPEO resin was produced using a microlayer coextrusion line available atCase Western Reserve University, Cleveland, Ohio. The rectangular stripsof multilayer PU PS370-200/PEO (70/30) film were stretched to six timesat 25° C. using a Sintech tensile tester. The resulting latentdeformation was about 150% in film length. The stretched film sample wasplaced in an environmental oven held at a temperature of 37° C. and 95%relative humidity. After 20 minutes in the environmental oven, thesample was removed and the dimensions of the film were measured. Thedimensional change of the film in machine direction was 46% as comparedto the stretched-film length.

Example 5

[0110] A microlayer film was produced using the method in Example 4,except a 16 layer PU/PEO (70/30) film was developed. The film wasstretched to produce a latent deformation of 180% in length. Thestretched film sample was placed in an environmental oven and held at atemperature of 37° C. and 80% relative humidity. After 20 minutes in anenvironmental oven, the sample was removed and the dimensions of thefilm were measured. The dimensional change of the film in machinedirection was 50%.

Example 6

[0111] A 70/30 blend of MORTHANE® polyurethane (PU) PS370-200 and PEOwas produced using the Haake laboratory twin screw extruder. Therectangular strips of film made of 70/30 blend were stretched to sixtimes at 25° C. The resulting latent deformation was about 100% inlength. The stretched sample was placed in an environmental oven held ata temperature of 37° C. and 80% relative humidity. After 20 minutes inthe environmental oven the sample was removed and the dimensions of thefilm were measured. The dimensional change of the film in machinedirection was 30% as compared to the stretched-film length.

Comparative Example 1 Activation of Sample Using Thermal Energy

[0112] The multi-layer PU PS370-200/PEO (50/50) film of Example 1 wasstretched to 6 times its original length at 25° C. using a Sintechtensile tester. The resulting latent deformation was about 330%. Thestretched sample was placed in a convection oven for 20 minutes at atemperature of 73° C. The sample was removed from the oven, and itsdimensions were measured. The dimensional change of the film in the MDwas 65% based on the stretched film length.

Comparative Example 2 Activation of Sample Using Thermal Energy

[0113] A 50/50 blend of PU PS370-200 and polyethylene oxide (PEO) wasproduced using a Haake laboratory twin screw extruder. Rectangularstrips of film, made from the 50/50 blend, were stretched to 6 timestheir original length at 25° C. The resulting latent deformation wasabout 170%. The stretched sample was placed in a convection oven for 20minutes at a temperature of 65° C. The sample was removed from the oven,and its dimensions were measured. The dimensional change of the film inthe MD was 63% based on the stretched film length.

[0114] Examples 7-10 demonstrate the effect of stretch rate, draw ratio,stretch temperature, stretch hold and cooling rate on the amount oflocked-in shape deformation.

Stretching Procedures to Impart Latent Deformation

[0115] An MTS Sintech 1/D instrument equipped with a 50-pound load celland an environmental chamber was used to stretch the samples to impart adesired amount of shape deformation. Samples of each film were cut 1″wide by 3″ to 4″ long and were labeled and marked in black ink withlines 20 mm apart. Samples were then placed in the grips of the MTSSintech 1/D instrument spaced 2″ apart and stretched a desired amount.Samples were stretched from 3× (i.e., three times the original length)to more than 6×, at a desired stretch rate. Stretch rates were either100 mm/min (i.e., the “slow” rate) or 500 mm/min (i.e., the “fast”rate). When necessary, the grips and sample were placed in theenvironmental chamber and heated to a desired temperature, which variedfrom about 37° C. to about 100° C., allowed to equilibrate, and thenstretched the desired amount at the desired rate.

[0116] Unless otherwise noted, after stretching, the sample was heldstretched at the stretching temperature for 1 minute. Then, the samplewas cooled by one of two methods. “Slow cooling” was one method whereinthe environmental chamber door was opened and the stretched sampleexposed to a fan until the sample had reached room temperature at whichpoint the sample was released from the stretched position and removed.The other method was “quenching,” wherein the environmental chamber doorwas opened and the sample was sprayed with a cooling agent (i.e.,Blow-Off freeze spray comprising 1,1,1,2-tetrafluoroethane) for a numberof passes while the sample was released from the stretched position andremoved from the chamber.

[0117] The distance between the lines was measured and recorded and newlines were marked in red 20 mm or 40 mm apart depending upon the samplelength. Latent, locked-in shape deformation, or percent latency, wasdefined as the change in length from the stretched sample to the initialsample, divided by the initial sample length, and multiplied by 100.

Example 7 Effect of Stretch Rate on the Amount of Locked-In ShapeDeformation

[0118] Rectangular strips of MORTHANE® PS370-200 were stretched using aslow stretch rate and a fast stretch rate. The strips were stretched upto 6 times their initial length at three separate temperatures, 25° C.,50° C., and 70° C. using a Sintech tensile tester (SINTECH 1/D) and anenvironmental chamber.

[0119] The results of the tests are given below in Table 1. TABLE 1Stretch Rate Results Temperature 25° C. 50° C. 70° C. Stretch Rate SlowFast Slow Fast Slow Fast % Latency 15 20 75 75 145 150

[0120] As can be seen in Table 1, the stretch rate did not significantlyeffect the percent latency of MORTHANE® PS370-200. However, thetemperature had a significantly effect on the percent latency ofMORTHANE® PS370-200.

Example 8 Effect of Draw Ratio on the Amount of Locked-In ShapeDeformation

[0121] Rectangular strips of MORTHANE® PS370-200 were stretched usingthree different draw ratios: 4×, 5×, and 6×. The strips were stretchedat three separate temperatures, 25° C., 50° C., and 70° C. using aSintech tensile tester (SINTECH 1/D) and an environmental chamber.

[0122] The results of the tests are given below in Table 2. TABLE 2 DrawRatio Results Temperature 25° C. 50° C. 70° C. Draw Ratio 4× 5× 6× 4× 5×6× 4× 5× 6× % Latency 15 15 25 80 120 75 125 — 150

[0123] As can be seen in Table 2, the draw ratio did not significantlyeffect the percent latency of MORTHANE® PS370-200.

Example 9 Effect of Stretch Temperature on the Amount of Locked-In ShapeDeformation

[0124] Rectangular strips of MORTHANE® PS370-200 were stretched usingthree different temperatures: 25° C., 50° C., and 70° C. The strips werestretched at two different draw ratios, 4× and 6×, using a Sintechtensile tester (SINTECH 1/D) and an environmental chamber.

[0125] The results of the tests are given below in Table 3. TABLE 3Temperature Results Temperature 25° C. 50° C. 70° C. Draw Ratio 4× 6× 4×6× 4× 6× % Latency 15 25 80 — 125 150

[0126] As can be seen in Table 3, the stretch temperature had asignificant effect on the percent latency of MORTHANE® PS370-200.

Example 10 Effect of Stretch Hold and Cooling Rate on the Amount ofLocked-In Shape Deformation

[0127] Rectangular strips of MORTHANE® PS370-200 were stretched atdifferent temperatures: 70° C. and 90° C. The strips were stretched at adraw ratio of 6×, using a Sintech tensile tester (SINTECH 1/D) and anenvironmental chamber. The samples were either slowly cooled or quenchedas described above. The samples were allowed to cool or quenched afterbeing held in a stretched position for one minute, and also withoutbeing held.

[0128] The results of the tests are given below in Table 4. TABLE 4Stretch Hold/Cooling Rate Results Temperature 70° C. 90° C. Stretch HoldLoad No Load Load No Load Cooling Method SC Q SC Q SC Q SC Q % Latency145 145 140 150 235 180 210 190

[0129] As can be seen in Table 4, the MORTHANE® PS370-200 samples had alarger amount of percent latency when slowly cooled after being held forone minute at a given stretch temperature and then allowed to cool asopposed to the samples allowed to cool without being held. Quenchingreduced the amount of time the samples were held and allowed to relax.Consequently, these samples generally had less percent latency. However,conclusions regarding the overall effect of quenching was hard todetermine from the above data.

[0130] The results of the MORTHANE® PS370-200 samples at 90° C. indicatethat stretch holding and cooling rate has a more significant effect onthe percent latency than similar samples tested at 70° C. In thesesamples, slow cooling produced the best results in percent latency.

[0131] While the specification has been described in detail with respectto specific embodiments thereof, it will be appreciated that thoseskilled in the art, upon attaining an understanding of the foregoing,may readily conceive of alterations to, variations of, and equivalentsto these embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

What is claimed is:
 1. A humidity responsive material having shapememory comprising: at least one shape deformable matrix material;wherein the humidity responsive material is capable of being deformed inat least one spatial dimension when exposed to one or more externalforces, is capable of maintaining a degree of deformation in at leastone spatial dimension once the external force is removed, and is capableof exhibiting a change, or percent recovery, in at least one spatialdimension when subjected to a humid environment.
 2. The humidityresponsive material of claim 1, wherein the shape deformable matrixmaterial comprises a polymer.
 3. The humidity responsive material ofclaim 2, wherein the shape deformable matrix material comprisespolyester-based thermoplastic polyurethane; polyether-basedpolyurethane; polyethylene oxide; poly(ether ester) block copolymer;polyamide; poly(amide ester); poly(ether amide) copolymer; polyvinylalcohol; polyvinyl pyrolidone; polyvinyl pyridine; polyacrylic acid;polymethacrylic acid; polyaspartic acid; maleic anhydride methylvinylether copolymers of varying degrees of hydrolysis; polyvinyl methylether copolymers of polyacrylic acid and polyacrylic ester; segmentedblock copolymer having one or more hard segments and one or more softsegments; or mixtures thereof.
 4. The humidity responsive material ofclaim 3, wherein the shape deformable matrix material comprises asegmented block copolymer comprising one or more hard segments and oneor more soft segments, where either the soft segment, the hard segment,or both contain functional groups or receptor sites that are responsiveto humidity.
 5. The humidity responsive material of claim 4, wherein thefunctional groups are selected from the group consisting of urea, amide,nitro, nitrile, ester, ether, hydroxyl, ethylene oxide, amine groups,carboxylic acid salts, sulfonic acid salts, ionic groups, and receptorsites having an unbalanced charge distribution formed from one or moreof the above groups.
 6. The humidity responsive material of claim 3,wherein the shape deformable matrix material comprises a segmented blockcopolymer comprising an elastomer.
 7. The humidity responsive materialof claim 6, wherein the elastomer is selected from the group consistingof polyurethane elastomers, polyether elastomers, poly(ether amide)elastomers, polyether polyester elastomers, polyamide-based elastomers,thermoplastic polyurethanes, poly(ether-amide) block copolymers,thermoplastic rubbers, styrene-butadiene copolymers, silicon rubbers,synthetic rubbers, butyl rubber, ethylene-vinyl acetate copolymer,styrene isoprene copolymers, styrene ethylene butylene copolymers andmixtures thereof.
 8. The humidity responsive material of claim 7,wherein the elastomer is selected from polyurethane elastomers orpoly(ether amide) elastomers.
 9. The humidity responsive material ofclaim 1, wherein the shape deformable matrix material comprises amulti-layer or micro-layer structure having separate layers of anelastomeric polymer and a non-elastomeric polymer.
 10. The humidityresponsive material of claim 1, wherein the shape deformable matrixmaterial comprises a blend of an elastomeric polymer and anon-elastomeric polymer.
 11. The humidity responsive material of claim10, wherein the non-elastomeric polymer is a moisture absorbing polymerand wherein the moisture absorbing polymer exhibits at least a 20%reduction in modulus when the material is exposed to a humidenvironment.
 12. The humidity responsive material of claim 11, whereinthe moisture absorbing polymer exhibits at least a 30% reduction inmodulus when the material is exposed to a humid environment.
 13. Thehumidity responsive material of claim 11, wherein the moisture absorbingpolymer exhibits at least a 50% reduction in modulus when the materialis exposed to a humid environment.
 14. The humidity responsive materialof claim 11, wherein the elastomeric polymer comprises thermoplasticpolyurethane, poly(ether-amide) block copolymer, thermoplastic rubber,styrene-butadiene copolymer, silicon rubber, synthetic rubber, styreneisoprene copolymers, styrene ethylene butylene copolymers, butyl rubber,nylon copolymer, spandex fibers comprising segmented polyurethane,ethylene-vinyl acetate copolymer or mixtures thereof.
 15. The humidityresponsive material of claim 11, wherein the moisture absorbing polymercomprises polyethylene oxide, polyethylene glycol, polyvinyl alcohol,polyvinyl pyrolidone, polyvinyl pyridine, or mixtures thereof.
 16. Thehumidity responsive material of claim 11, wherein the shape deformablematrix material comprises from about 5% to about 90% by weight moistureabsorbing polymer.
 17. The humidity responsive material of claim 11,wherein the shape deformable matrix material comprises from about 10% toabout 60% by weight moisture absorbing polymer.
 18. The humidityresponsive material of claim 11, wherein the shape deformable matrixmaterial comprises from about 10% to about 95% by weight elastomericpolymer.
 19. The humidity responsive material of claim 11, wherein theshape deformable matrix material comprises from about 50% to about 70%by weight elastomeric polymer.
 20. The humidity responsive material ofclaim 1, wherein the material exhibits at least a 20% reduction inmodulus when the material is exposed to a humid environment.
 21. Thehumidity responsive material of claim 19, wherein the material exhibitsat least a 30% reduction in modulus when the material is exposed to ahumid environment.
 22. The humidity responsive material of claim 19,wherein the material exhibits at least a 50% reduction in modulus whenthe material is exposed to a humid environment.
 23. The humidityresponsive material of claim 1, further comprising a non-activatableadditional material selected from the group consisting ofnon-elastomeric polymers, tackifiers, anti-blocking agents, fillers,antioxidants, UV stabilizers, polyolefin-based polymers, and mixturesthereof.
 24. The humidity responsive material of claim 23, wherein thehumidity responsive material comprises from about 40 to about 99.5weight percent of shape deformable polymer and from about 60 to about0.5 weight percent of additional non-activatable material.
 25. Thehumidity responsive material of claim 23, wherein the humidityresponsive material comprises from about 60 to about 99.5 weight percentof shape deformable polymer and from about 40 to about 0.5 weightpercent of additional non-activatable material.
 26. The humidityresponsive material of claim 23, wherein the humidity responsivematerial comprises from about 80 to about 99.5 weight percent of shapedeformable polymer and from about 20 to about 0.5 weight percent ofadditional non-activatable material.